The present invention relates to an apparatus and method for acquiring and processing images, particularly of moving media, and for the validation of such media. The invention has particular application in the field of self-service terminals (SST) and in detection of forged banknotes and similar media. In its broader aspects the invention has application in verifying or confirming the source or validity of other items or products.
A growing number of financial and similar transactions are carried by means of self-service terminals (SSTs) such as automated teller machines (ATMs). Many transactions involve the deposit of media such as banknotes into the SST to pay for some service or product, or simply to credit the deposit to a user""s bank account. Therefore such SSTs require a media recognition mechanism to recognize and determine the value of the deposited media, and to validate the media and detect forged or inappropriate media, such as forged banknotes or foreign currency.
A number of systems currently exist for the validation of banknotes based largely on the identification of specific anti-fraud features incorporated in the notes. Features which may be used by SSTs to verify banknotes include the detection of magnetic xe2x80x9cbar codesxe2x80x9d on the notes; watermarks; response of the notes to ultraviolet light; the size and shape of banknotes; interference patterns generated by light reflected from the banknotes; the electrical capacitance of the banknotes; and various other features. However, existing systems suffer from the disadvantages that particular anti-fraud features are found in certain denominations or currencies of banknotes but not in others, and thus a system designed to detect, say, Swiss Francs may not be able to validate US Dollars; and that a suite of different sensors is typically required to detect a range of characteristics of the banknotes in question. Thus, SSTs destined for different markets must be designed and configured individually, and modified if there is any change to the design of the local currency.
A further disadvantage is that existing validation systems typically require the banknote to be stationary, extending the time necessary to execute a transaction.
It is among the objects of embodiments of the present invention to obviate or alleviate these and other disadvantages of existing media validation systems. This may be achieved, in part, by making use of the optical properties of banknotes, in particular the complex colors of the inks used in printing banknotes: a feature which is almost universal among banknotes is the high quality of ink used. Colors of banknotes are typically produced by a xe2x80x98purexe2x80x99 color ink, rather than a blend of different colors such as red, yellow, and blue. Embodiments of the present invention enable these xe2x80x98purexe2x80x99 colors to be detected on banknotes, or indeed any other media. A similar principle may also be utilized in verifying the source of a particular product of almost any form, by analysis of particular optical properties of the product, as described below.
According to a first aspect of the present invention there is provided a method of imaging media, the method comprising the steps of:
a) locating media in the path of an imaging means and a variable interference filter (VIF), the filter being disposed between the media and the imaging means;
b) acquiring an image of at least a region of the media;
c) processing the image to determine a selected characteristic of the media;
d) moving the media relative to at least one of the filter and imaging means;
e) acquiring a further image of at least a region of the media; and
f) processing the further image to determine a selected characteristic of the media.
The image thereby consists of data relating to the intensity of the particular wavelength of light passed by the filter. In the case of banknotes, the intensity of each wavelength band will vary depending on the presence or absence of ink of a particular color or composition; which factor will in turn aid in determination of the denomination, currency, and acceptability of the banknote. Although reference is made herein primarily to the handling of banknotes, those of skill in the art will realize the invention has applicability in relation to other forms of valuable media, and indeed to any product which is colored or possesses particular light reflecting qualities.
Processing of the images may take place in sequence, that is, each image is processed prior to acquisition of a further image; or, preferably, all images are processed subsequent to the end of the acquisition steps.
Preferably, the imaging means comprises a monochrome CCD camera. This acquires the image in a digital format which is relatively easy to process and manipulate. Use of a monochrome camera ensures that no color filtering of the image occurs other than that provided by use of the filter; color CCD cameras typically detect images by detecting the intensity separately of red, green, and blue wavelengths of light. However, alternative imaging means may be used, for example other forms of camera or light intensity sensors; the acquired image is not necessarily human readable or recognizable, and may take the form of a digital data stream.
Preferably, the VIF is a linear VIF. A linear VIF is a narrow bandpass filter which passes light according to a wavelength that varies linearly along the length of the filter but is constant across its width. A typical linear VIF may pass light which varies from 400 nm to 700 nm along the length of the filter to cover the visible spectrum; or from 400 nm to 1000 nm to include infra-red. Of course, any desired range of wavelengths may be utilized.
The above-described method using a VIF is capable of acquiring image information over the whole area of a banknote over the whole visual spectrum (if desired) with a high spatial resolution, while the banknote is moving. That is, as a region of the banknote moves with respect to the filter and the imaging means, a sequence of images will be acquired; and each image will contain information relating to the intensity of light of a different part of the spectrum: if desired the entire note may be imaged across the whole spectrum passed by the VIF.
Preferably, the step of processing the acquired images may be used to assemble selected types of spectrum information which may be used for identification of banknotes, or simply to isolate information of interest for a particular purpose from the full amount of acquired data. For example, the presence or absence of a particular ink color may be determined from the image of the note acquired at a specific wavelength. As each image acquired by means of a VIF as described above includes data from a number of wavelengths, to obtain an image of the whole note at a single wavelength, it is necessary to manipulate the acquired images. Further, the whole range of acquired data may not be required for some applications; unwanted data may be discarded in processing to increase the speed of the remaining operations.
Preferably also, the method further includes the step of comparing some part of the acquired data against reference data. This enables an identification of the banknotes to be carried out, and if the note is not recognized, to be rejected. For example, processed images of a single wavelength may be compared against a reference image of a banknote at the same wavelength. Alternatively, or in addition, the full spectrum information of a note over a selected area of the note, such as the name of the issuing bank, or the denomination of the note, may be compared against a reference portion of a genuine note.
Conveniently, a number of features of the method may be varied. The rate of acquisition of images and the speed of movement of the media relative to the filter or imaging means may both be varied independently to alter the spatial and spectral resolution of the acquired images, depending on the desired purpose of the imaging. Also the processing step and comparison steps may be varied to adapt the method for use with different banknotes or different types of media, each type having its own diagnostic characteristics. Most conveniently, these steps are implemented by computer programs, thus making these modifications relatively straightforward to effect.
According to a second aspect of the present invention there is provided a method of detecting forged media, the method comprising the steps of:
a) locating media in the path of an imaging means and an optical filter, the filter being disposed between the media and the imaging means;
b) acquiring an image of at least a region of the media;
c) processing the image to determine a selected characteristic of the media; and
d) comparing the acquired image against a reference image derived from genuine media.
Forged media, such as banknotes, do not reproduce precisely the spectral and spatial distribution of color over the banknote, due to the use of different inks and printing presses, and so may be detected in this way. Other products, for example xe2x80x9cdesignerxe2x80x9d clothing or pharmaceutical products will feature particular dyes, and so genuine products may be distinguished in this way from fake products.
According to a third aspect of the present invention there is provided an apparatus for imaging media, the apparatus comprising:
imaging means for acquiring an image of an object;
a variable interference filter for passing light only of specific wavelengths from an object to the imaging means; and
image processing means for processing the acquired images and extracting selected data therefrom.
Preferably, the apparatus further comprises media transport means for moving the object relative to the filter means and the imaging means. This enables the full available range of spectral and spatial data to be acquired; for example, images of an entire banknote may be acquired over a 400 nm-700 nm range.
Preferably, the imaging means comprises a CCD camera. Preferably also, the filter means comprises a linear variable interference filter (VIF). Preferably also, the image processing means comprises a computer provided with appropriate computer programs.
According to a fourth aspect of the present invention there is provided a self-service terminal (SST) comprising:
media input means for transporting media, such as banknotes or the like, into the SST;
imaging means for acquiring an image of the media;
filter means for passing light only of specific wavelengths from the media to the imaging means; and
image processing means for processing the acquired images and extracting selected data therefrom.
According to a fifth aspect of the present invention there is provided a method of operating a self-service terminal (SST), the method comprising the steps of:
depositing media into the SST;
locating the media in the path of an imaging means and an optical filter, the filter being disposed between the media and the imaging means;
acquiring an image of at least a region of the media;
processing the image to determine a selected characteristic of the media;
comparing said selected characteristic of the entered media against a reference characteristic of acceptable media; and
rejecting or accepting the deposited media accordingly.
According to a sixth aspect of the present invention, there is provided a method of characterizing objects according to specific optical properties, the method comprising the steps of:
locating the object in the path of an imaging means and an optical filter, the filter being disposed between the object and the imaging means;
acquiring an image of at least a region of the object;
processing the image to determine a selected characteristic of the object;
comparing said selected characteristic of the imaged object against a reference characteristic of standard objects; and
characterizing the imaged object accordingly.